Snowboard boots generally fall into one of two categories: "hard-style" or "soft-style" boots. Hard snowboard boots are the preferred boot for downhill riding. The construction of hard snowboard boots is similar to that of conventional ski boots. Plate bindings are used for attaching the hard boots to the snowboard.
Soft-style snowboard boots are the preferred boot for freestyle riding. The construction of the soft boot design is characterized by a flexible boot upper which permits high lateral mobility to accommodate the ankle and calf movement of the rider during freestyle maneuvers. Common binding types for attaching the soft-style snowboard boot to the snowboard include external strap bindings and step-in bindings.
It is well recognized in the art that soft-style snowboard boots require support in the calf region in order to lock out forward extension of the ankle in order to facilitate tipping the board on edge when executing a back side or heel side turn.
In the past, this support was provided by the high back structure of conventional strap bindings. The high back structure effectively locks out the forward extension movement of the ankle, while side-to-side rotation of the ankle and foot is permitted (as allowed by the flexibility of the boot/ankle). Without this flexibility, the rider's ability to optimally control board position and bodily stance is diminished. This is especially detrimental to "freestyle" riding, where quick turns and stunts require a high degree of side-to-side ankle/foot flexibility.
In the case of step-in bindings, there is no external high back. Therefore, an essential feature to the design of a soft-style boot for step-in bindings is the relocation of the external high back support structure found on conventional (strap-type) bindings to the interior of the boot. This structure allows the rider to efficiently apply a rearward force (towards the back edge of the snowboard) which is critical in providing control while riding. The high back is fixed at a particular angle in relation to the board, such that a force applied "backwards" to the high back (relative to the boardrider), with the board pivoting about an axis through the heel side edge, will pull the front of the board upwards. The rider simply leans backwards, pushing the high back backwards, which then "tips" the board up onto the heel side edge. Without such a structure, the rider would have to pull the toe edge of the board upwards using his leg muscles. The high back structure effectively "locks out" the forward extension of the ankle. However, as the boot is not attached to the external high back, lateral and medial rotation of the ankle/foot is not inhibited by the high back.
The internal high back support structure should provide similar effectiveness of ankle lock out as an external high back while also allowing relatively free side-to-side rotation of the ankle/foot. Thus, the provision of an integral structure in a soft-style snowboard boot which provides similar support as an external high back while still allowing lateral/medial flexibility would be a highly desirable feature.
For the case of conventional strap bindings with external high back support, the amount of forward lean is determined by the angle of the external high back, which is not itself attached to the boot. Therefore, lateral/medial rotation of the ankle/foot does not affect the amount or degree of forward lean imparted by the high back, and vice-versa. Forward lean and lateral/medial ankle/foot rotation are effectively isolated from one another. Without this isolation, the rider's freedom of movement/board stance and degree of control are diminished. A high back/forward lean structure that is integral to the boot must effectively retain this independence between forward lean and lateral/medial ankle/foot rotation.
From published European Patent Application EP 0 646 334 A1, there is disclosed a high back support insert for a soft-style snowboard boot which is adapted to be placed between the flexible outer boot portion and the soft padded inner boot portion. The insert includes a heel cup/foot bed portion which is pivotally connected to an upper high back portion at the height of the ankle about an axis extending in the longitudinal axis of the boot plane. A pair of lengthwise adjustable straps connect opposite sides of the foot bed portion (at the ball of the foot region) to respective opposite sides of the high back. A shortening adjustment of the straps provides a change in the forward lean of the boot insert by pulling the upper high back portion forwardly toward the toe end of the heel cup foot bed portion of the boot insert.
Blax of Germany is currently selling a version of this type of high back soft boot insert under the name of I-SPINE. The Blax system utilizes a single direction tension adjustment via a ladder strap that runs vertically up the back of the ankle. In the Blax design, the fixed pivot location between the high back and heel cup means that the presence of high back is always "felt" by the rider. In toe side turns, the fixed pivot restrains the high back and does not allow it to follow the forward lean of the rider's ankle. In view of the fixed pivot feature, this design feels mechanical and limiting as it does not closely mimic the rolling articulation of the foot and ankle. It is noted that the ankle joint has a very limited amount of side-to-side angular rotation. The side-to-side flexibility of the ankle/foot is mostly achieved by rotation/articulation of the structure of the foot.
Accordingly, an ankle support device for a soft-style snowboard boot which provides high back support needed for heel side turning and which also closely approximates the rolling articulation or the ankle and foot during side to side movements and toe side turning would constitute a significant advance in the art.